The present invention relates to an exposure apparatus for use in producing semiconductor devices and liquid crystal displays.
In a photolithography process in the manufacture of semiconductor devices and liquid crystal displays, a projection exposure apparatus is used for forming a fine circuit pattern on a semiconductor layer or a metallic wiring layer. In the projection exposure apparatus, a reticle or a photomask (hereinafter, frequently referred to simply as "reticle") having formed thereon a circuit pattern is provided on a reticle stage, and a wafer stage having provided thereon a semiconductor wafer or a glass substrate (hereinafter, frequently referred to simply as "wafer") with a photoresist coating is moved relative to the reticle along an x-axis and a y-axis in a two-dimensional plane, to thereby transfer the circuit pattern formed on the reticle to a predetermined area on the wafer.
Types of exposure apparatuses can be roughly classified as a projection exposure apparatus of a step and repeat type in which a pattern on a reticle is projected through a projection optical system as a reduced pattern image and the reduced pattern image is formed on each exposure field on a wafer, and a scanning projection exposure apparatus of a so-called step and scan type in which a part of a pattern on a reticle is projected through a projection optical system on a wafer while moving the reticle and the wafer synchronously in predetermined scanning directions, to thereby transfer the pattern on the reticle to the wafer.
In conventional exposure apparatuses, such as mentioned above, main components of the exposure apparatus, i.e., an illumination optical system, a mask stage and a substrate stage, are supported relative to an installation surface for the exposure apparatus by four support legs. It is preferred that these components be maintained precisely horizontally. However, it is extremely difficult to maintain these components of the exposure apparatus on a horizontal plane by adjusting the lengths of four support legs, so that dynamic stability of the entire exposure apparatus is likely to be poor. Further, the area of the installation surface for the exposure apparatus, which is included within four support legs, is relatively large.